Purdue Extension Sciences AS-573-W Managing Internal in and Kate Hepworth, Animal Sciences Student; Mike Neary, Extension Sheep Specialist; Terry Hutchens, Extension Associate for Production, University of Kentucky

Internal parasites are a significant threat facing However, by developing a parasite control plan aimed today’s small producer. Problems associated at Haemonchus, the majority of other dangerous with parasites, particularly those of the gastrointestinal parasites will be controlled as well. tract of sheep and goats can cause irreversible damage Lifecycle or even death to the animal, reduced performance and Sheep and goats are generally affected by the same economic loss for the producer. that are parasites, although certain parasites may affect one overburdened with parasites can be hindered in their species more severely than the other, and treatment reproductive performance, experience reduced growth methods may vary between sheep and goats. In order rates, and become less productive overall, whether to know how best to prevent future problems with their purpose be meat, fiber, or milk. Prevention and parasites and control current , it is control of the parasites that infect sheep and goats are necessary to understand the general life cycle of the becoming increasingly difficult due to generations of parasites most common to sheep and goats. overuse and improper use of the available dewormers, which results in increasing resistance by parasites to common . This paper will be used to give producers a general understanding of the parasites that affect their animals, how they live, and methods that can be used to lower their costs and losses due to parasite infestations. Sheep and goats are affected for the most part by the same parasites. By far the most deadly internal parasite to small in the Midwestern United States is the gastrointestinal roundworm Haemonchus contortus, also known as the barber pole worm and a variety of other names. Haemonchus contortus is a blood sucking parasite that can cause severe , protein loss and death in goats and sheep, and thus is the most important to control. Some other parasites that affect sheep and goats are those of the family, particularly Teladorsagia circumcincta and Trichostrongylus axei, and the protozoa coccidia. Haemonchus contortus is the most dangerous parasite to sheep and goats in many parts of the United States, although other parasites may be Figure 1: The lifecycle of a gastrointestinal parasite. This image is important in different regions outside the Midwest. courtesy of Virginia Tech Cooperative Extension.

Purdue University Cooperative Extension Service, West Lafayette, IN 47907 Haemonchus has a lifecycle that takes approximately 21 days to complete (see Figure 1). The cycle begins when the larvae in the infective L3 stage of development are ingested from the grass and travel to the abomasum, or true stomach, of the host. Once in the abomasum the larvae will follow one of two paths. They may proceed with further larval stages and the eventual development into adults, or they will go into hypobiosis. This is an inhibited, or arrested development state, that occurs when conditions are not conducive for the entire life cycle to be complete. When the L3 stage larvae enter the abomasum, provided that environmental conditions are favorable, they will molt into the L4 stage of larval development and will then molt once more into adults. Factors that induce the molting of the L4 larvae into adults include: greening of grass, a rise in environmental temperature, rain following a drought period, increased estrogen Figure 2: This image shows magnified eggs of Haemonchus Contortus. levels in the host, and possible even a photoperiod stimuli. Once the molt into an adult form is complete kidding and begin to produce eggs. This phenomenon adults then begin to lay eggs in the abomasum. is called the “periparturient rise” in fecal egg counts In the case of Haemonchus and Ostertagia, the L4 (will be discussed later). The eggs laid in the larvae can go into arrested development, or hypobiosis. abomasum are expelled from the body via the feces. Hypobiosis is a period of dormancy that occurs when Eggs in the feces generally remain inactive for a few the environment is not conducive to the lifecycle of days in the environment, until the environment and these parasites. Larvae in different regions may go into temperature become favorable for the development of hypobiosis in different times during the year, these eggs into larvae. The larvae hatch from the egg depending on the environment. For example, in the and then emerge from the pellets and move through Midwestern states, Haemonchus larvae will likely larval stages L1, L2 and L3 of development. Once the become dormant during harsh winters. In southern larvae reach the L3 stage, the infective stage, they parts of the country, hypobiosis may occur when the emerge from the fecal pellet and climb up onto blades weather is too hot or dry for larvae to survive. of grass (see Figure 3) where they wait to be ingested During hypobiosis the L4 larvae hibernate in glands by a grazing animal, thus completing the lifecycle. In in the abomasum without developing further or causing problems for the host. They remain metabolically inactive until they receive signals that indicate it is time for them to resume development and then begin to lay eggs. The signals that spur the L4 larvae to come out of hypobiosis are the same signals mentioned above that indicate to them to develop in the first place. Once larvae leave hypobiosis, they resume the normal lifecycle and begin to lay eggs. Haemonchus adults require about 14 days to begin laying eggs (see Figure 2) in the stomach after reaching adulthood. The Haemonchus adult female can lay up to 5,000 eggs per day, yet another reason why Haemonchus is so difficult to control and so dangerous to sheep and goats. Females that have gone through hypobiosis over the winter generally resume Figure 3: This image depicts larvae inside a droplet of water on a blade development two to four weeks prior to lambing or of grass.

Purdue Extension • Knowledge to Go  order for the larvae to emerge from the fecal pellet in many eggs at a young age due to the periparturient egg which it was expelled from the body, the environment rise of the ewe or doe. The lambs and kids will begin has to be in a condition that keeps the pellet moist and to develop some immunity to parasites around six to pliable. Optimal conditions for the L3 larvae to emerge eight weeks of age, provided that they do not reach from the pellet are warm, wet conditions, like those pathogenic levels of parasites in their system before that usually occur in the early spring. this time. Lactating ewes and does on pasture follow An important characteristic of these larvae that must the lambs and kids with slightly increased resistance to be taken into account when designing a parasite . Lactating animals are often in a negative control plan is that the L3 larvae can survive on energy balance, and therefore are weaker and less able pasture for extended periods of time, making pasture to resist the effects of parasites on their body. Goats at management a key component in the prevention and any reproductive stage are more susceptible to control of parasite infection. The L3 larvae can survive parasitic infection than sheep. on pasture for up to 90 days in the summer, and up to Ewes or does in late gestation, and for a short period 180 days in the fall or winter. The Haemonchus larvae after parturition lose much of their resistance to thrive in temperatures ranging from 70° to 80° parasites due to hormonal and photoperiod effects. Fahrenheit where there is an average of approximately During this period, the ewe or doe is no longer able to 2 inches of rainfall per month. Extremely hot or dry resist worm development or egg production. This environments will cause egg laying to stop, but the phenomenon is termed the “periparturient egg rise,” larvae can survive temperatures below 32° F. and is a critical time in the parasite control plan. It is Ostertagia larvae prefer cooler temperatures, with particularly important because it coincides with a time their optimum temperature for development being when the number of susceptible animals (kids or around 40° Fahrenheit. These larvae are very resistant lambs) increases significantly. Finally, mature dry to adverse winter conditions, and can over-winter on ewes are the least susceptible to parasitic . pasture. These animals have some immunity due to their age, Animal Susceptibility and are under no real stress to their system that could lower their body’s ability to resist parasitic infections. Individual goats and sheep vary in their degree of Goats of any age have little natural resistance or susceptibility to Haemonchus and other parasites. resilience to parasitic infection. Some animals, by means of their genetics, are much more resistant or resilient to parasitic infections, and Recognizing Parasitic Infections can survive parasite levels without showing any When animals are heavily burdened with parasites, symptoms while another animal may be killed by that there are a variety of symptoms that can be used to level of . This genetic resistance can be used identify if an animal is infected with parasites, and when selecting breeding stock, since a herd that which parasites are causing the problem. Some general exhibits more innate resistance to parasites will cost symptoms typical of parasite infections are diarrhea, less to maintain and will ultimately be more profitable weight loss or reduced weight gain, unthriftiness, loss to the producer. of appetite, and reduced reproductive capacity and Animal age and stage of development also have a performance. significant impact on the susceptibility to parasites. As In the case of Haemonchus, anemia and edema, or animals age, they are exposed to more and more swelling, are key symptoms. The Haemonchus parasite parasites and develop some immunity to infection. can consume up to 1/10th of an animal’s total blood This is more likely with sheep than with goats. volume in a day. Anemia is most easily identified in Resistance describes an animal’s ability to resist small ruminants by the color of the mucous membranes, infection from parasites, while resilience describes the particularly those in the lower eyelid. A normal animal animal’s ability to withstand infection from parasites will have healthy, red mucous membranes, while one once it has occurred. heavily burdened with Haemonchus will exhibit light Young animals that are growing and are on pink or white membranes. Edema may also occur in continuous permanent pasture are the most susceptible animals heavily burdened with Haemonchus. This to parasites. These animals have very low levels of accumulation of fluid will be most obvious as a immunity, and are extremely susceptible to infection swelling in the lower jaw, a condition known as “bottle from parasites on pasture. They are also exposed to jaw” (see Figure 4). Diarrhea is not a common

Purdue Extension • Knowledge to Go  and goats make them much more susceptible to parasites than other species. Sheep tend to graze much closer to the ground than other animals, and also show little aversion to grazing in areas with high fecal contamination. These two characteristics drastically increase the numbers of larvae that sheep are exposed to and also the number that they are likely to ingest. Although parasite problems cannot be entirely eliminated by good pasture management, using good rotational grazing techniques combined with an efficient anthelmintic program should significantly lower the parasite problem in the herd. As was described in a previous section, the infective L3 larvae of Haemonchus can survive on pasture for Figure 4: This picture shows a goat with bottle jaw, a main symptom extended periods of time. The goal of pasture of parasitic infection. This picture is courtesy of Dr. Ray Kaplan, DVM, management is to allow the pastures enough time to University of Georgia. rest so that lower numbers of larvae are infective and symptom of Haemonchus infection, although it has will not be a problem to the grazing animals. There are been known to occur in some cases. varying ideas of what a “safe” pasture consists of, but In order to make a definitive diagnosis of the a general rule is that a pasture is considered relatively parasite burden of your herd, it may be necessary to free from Haemonchus if it has been tilled or burned enlist the help of a veterinarian or a laboratory. Fecal since the last time that sheep and/or goats grazed the egg counts can be done to measure the number of eggs land. The land would also be considered safe if it has shed in the feces of a random sample of animals in the been grazed by other species of animals (especially herd. Fecal egg counts are mainly useful in determining cattle or horses), or if three months have passed since the level of contamination on the pasture, since these it was last grazed during the spring or summer and if numbers vary significantly from herd to herd and six months have passed since it was last grazed over animal to animal. Some herds may be quite resistant to the winter. Pasture that has had a crop of hay removed parasites, and will have large fecal egg counts with no is also considered safe. significant health problems. Other herds may be very Allowing pasture to rest stops the land from having susceptible to parasites and a low egg count can still any more parasites deposited on it, and it also allows be indicative of some problem. Fecal samples can also for new growth, which lowers the risk that sheep and be used to determine which species of parasite is goats will ingest the larvae present in the pasture. infecting the herd in question. In some cases blood When pasture is overgrazed, sheep, which tend to tests can also be used as a diagnostic tool for parasitic graze close to the ground anyway, are exposed to even infection. more of the larvae that live low down on blades of Control grass. When done properly, pasture management can reduce the number of parasites that sheep and goats are The main goal in attempting to control Haemonchus exposed to. The best way to avoid pasture related and other internal parasites is to break the life cycle, parasite problems is to avoid overgrazing areas of which can be done in a variety of ways. The three pasture, and to implement a rotational grazing system. methods that will be discussed in this publication are Rotational grazing implies that once a pasture has been use of anthelmintics, animal management, and pasture grazed, animals are rotated to another paddock and the management. Using a combination of these three will pasture is allowed a rest period. If cattle or horses usually give the best results, and the best chance of grazing can be incorporated into the grazing system, breaking the life cycle of Haemonchus in your herd. parasite contamination can be reduced even further. Pasture Management Safe pastures can also be created by planting or Pasture management is a key aspect in breaking the utilizing summer annual forage crops. Examples of lifecycle of internal parasites. As mentioned in the these would be sorghum x sudan hybrid forages. These previous section, infective larvae can survive for long forages grow quite tall and animals graze at shoulder periods of time on pasture. The grazing habits of sheep or higher height (see Figure 5). This reduces the

Purdue Extension • Knowledge to Go  sheep and goat producers is that there are very few anthelmintics that are actually approved by the FDA for use in small ruminants. The second problem is the resistance that parasites have developed to many anthelmintics. Resistance occurs when a drug is overused and the parasites develop a tolerance to the drug, making it no longer effective in killing them. Resistance makes it very difficult to effectively control Haemonchus because it lowers the number of options available to treat the parasite, especially since resistance to one drug often means that a parasite will be resistant to all drugs in that compound class. Resistance will be discussed in more depth in a later section. Figure 5: This picture shows a goat that is browsing, or grazing at Anthelmintics can be used in conjunction with shoulder-height. rotational grazing and proper pasture management (discussed in a later section) to lower the number of opportunity to ingest larvae. Also, goats are natural parasites that the herd is exposed to. It used to be a browsers, and browsing forages or brush well above recommendation to deworm animals and then rotate to ground level has the same effect. a new pasture. More current thinking is this practice Anthelmintics allows eggs from resistant parasites to have a Anthelmintics (see Figure 6) are drugs that either kill competitive advantage on the pasture rotated on, thus egg laying adults, or kill larvae before they become enhancing resistance development. After treating adults and become capable of laying eggs. While some animals for parasites they should be left in original anthelmintics are effective in killing Haemonchus, pasture for a couple of days before rotating. Under there are two major problems that arise when using some circumstances, it is recommended to keep anthelmintics. The first problem that affects mainly animals on a dry lot for 12 to 24 hours after deworming. This ensures that the eggs and larvae that survived the anthelmintics are not deposited on safe pasture. The decision whether or not to dry lot animals after treating with anthelmintics should be based on the season, the type of anthelmintics used, and the diet of the animals. It is usually more important in goats than sheep, since goats tend to metabolize anthelmintics faster than sheep and have a faster passage rate through the intestinal tract. Ewes and does should also be dewormed prior to breeding and approximately two weeks prior to and one week after lambing or kidding to help combat the pre-parturient egg rise. There may also be a need for treatments throughout the grazing season, depending on the specific situation and condition of your herd. The suggestions described in this section are up to the discretion of the producer and veterinarian. There are a variety of methods that can be used to monitor the parasite levels in one’s herd, and also to lower the chance of developing drug resistant parasites in your herd. There are three main classes of drugs that are currently used as anthelmintics in sheep and goats. Figure 6: This picture shows a variety of different anthelmintics. This These three are avermectins, benzimidazoles, and picture is courtesy of Dr. Lisa Williamson. imidothiazoles. These classes contain all of the

Purdue Extension • Knowledge to Go  anthelmintics that are used in controlling and treating As mentioned previously, extra-label use requires parasites in goats and sheep. the producer to work closely with a veterinarian to get Benzimidazoles a prescription for the desired drug, as well as the proper doses and withdrawal times when using the Benzimidazoles contain the anthelmintics anthelmintics. Through extra-label use, goats can be , fenbendazole, , , treated with , , levamisole, and and oxibendazole. Fenbendazole is approved for use in moxidectin. There are more anthelmintics approved goats, and albendazole is approved for use in sheep. for use in sheep, so there is less necessity for extra- This class of anthelmintics is also known as the white label use than with goats. drenches. While benzimadoles have a high margin of safety (meaning that it can safely be given at double or Administration of Anthelmintics triple the labeled dose) and are effective against many Anthelmintics can be administered to animals by species of intestinal parasites, their efficacy against varying means, with the most common being in the Haemonchus is fairly low. The other problem with form of oral drenches. Oral drenches are thick liquid benzimidazoles, which is more pronounced in this class suspensions of the anthelmintics that are deposited into of drugs than in others, is that if a parasite is resistant the back of the animal’s mouth (see Figure 7). to one of the benzimidazoles, the resistance is most Some anthelmintics are available in the injectable likely wide spread among all of the drugs in this class. form, but these are not generally recommended for use Avermectins in small ruminants. It is particularly important when The main drugs in this class are ivermectin and moxidectin. Both drugs are effective against Haemonchus in normal situations, but they are only approved by the FDA for use in sheep, and requires extra-label use in goats. Extra-label use requires that the producer work with a veterinarian to get a prescription for the desired drug, as well as the proper doses and withdrawal times when using the anthelmintics. Sheep should be given the sheep drench form of ivermectin and moxidectin, and goats should receive a higher dose. Imidothiazoles The most important drug for sheep and goats in this class is levamisole. Levamisole is approved for use in sheep and is also shown to be very effective against Figure 7: This picture shows an oral drench being administered to a goat. Haemonchus. There is less of a resistance problem to levamisole than there is to benzimidazoles. using drugs not labeled for use in sheep and goats that Extra Label Use of Anthelmintics the concentration of the active substance be considered Many drugs that are not approved for use in sheep when determining the appropriate dose for the animals. and goats are perfectly safe to use, they remain It is also necessary to realize that sheep and goats unapproved however because of the expense metabolize many anthelmintics at different rates, with associated with getting FDA approval for drugs. The goats usually metabolizing the drugs faster and often small ruminant industry is not prominent enough in requiring a larger dose. this country to warrant the government or the drug When using products that are not approved for sheep companies expending the money necessary to do the and goats, it is imperative that the amount being given research and approve the drug. The goat industry is in fact the recommended dose for sheep or goats, not suffers even more than the sheep industry from this the species for which the formula is marketed. Some perspective, because there are even fewer products may be marketed for cattle as injectable or anthelmintics approved for use in goats. However, pour on, but will be ineffective if administered to although some drugs are not approved for use in a sheep or goats in this manner. Pour-on anthelmintics particular species, they can still be used to treat are formulated to be absorbed through the skin of parasite infections through extra-label use. cattle, but do not absorb in therapeutic amounts

Purdue Extension • Knowledge to Go  through sheep and goat skin due to the wool and hair herd. Samples should be taken at the time of deworming of these species. It is also important that drenches are and then again 10 to 14 days from the same animals mixed in the proper way and administered while they after treating with an anthelmintic. In order for an are still effective. If drenches are not mixed properly, anthelmintic to be considered effective, there should they may settle out, and the animal will not receive the be at least a 95 percent reduction in the number of effective amount of the anthelmintics. It should also be eggs between the two samples. If the test shows a common practice to check the expiration date of a reduction of less than 95 percent between the two product before administration. samples, it is probably time to rotate to a new class Parasite Resistance to Anthelmintics of drugs (see Figure 8). Resistance is one of the main reasons why parasites, Haemonchus contortus in particular, are such a huge problem for small ruminant producers. Producers may find one method or anthelmintic that appears to effectively control parasites in their herd, but the efficacy of anthelmintics can be significantly lowered when resistance develops. Resistance is very difficult to overcome because it reduces the number of anthelmintics available to treat the herd and may last for years. Resistance to anthelmintics has developed as a result of years of overuse and improper dosing with available anthelmintics. When producers continuously deworm their herd with the same anthelmintics, fewer and fewer parasites are killed with every treatment, and Figure 8: This picture shows people in a lab reading the results of a genetic selection for resistant parasites occurs. This Fecal Egg Count Reduction test. resistance occurs mostly when animals are under- dosed, meaning that the amount of anthelmintics Avoiding Resistance administered to the animal is not enough to kill a significant number of parasites. The parasites that are First and foremost, resistance can be prevented by resistant to the drug then begin to reproduce and the making certain that herds are all dosed for the heaviest number of resistant parasites in the animal continues to animal in the class, with does, bucks, and kids each multiply until that particular drug is no longer effective making up a separate class within the herd. Most at all. anthelmintics (except levamisole) have a wide safety margin, so it is not dangerous to give the smaller Checking your herd for resistance animals a dose higher than the recommended amount. If a producer suspects that resistance may be present If lambs or kids are included in the herd, all of the in his herd, there are a few things that need to be lambs or kids should be dosed according to the weight considered. Anthelmintics can be ineffective for a of the heaviest lamb or kid in the herd. It is imperative variety of reasons, which should be ruled out before that the equipment being used to administer anthelmintic resistance is determined as the root of the problem. medication to animals is calibrated properly, and that Improper dosing is a major reason for the reduced or the compound itself is effective, not out of date, total lack of efficacy in anthelmintics. Before improperly stored or ineffective due to resistance. administering the dewormer, it is important to make Producers can avoid resistance in their herd by not sure that the dosing gun is calibrated properly and purchasing animals that already show signs of having that the proper dose is being delivered to the animal. resistant parasites. If these animals must be purchased, When all of these possibilities for ineffectiveness they should be aggressively treated for parasites, and of a dewormer can be ruled out, a Fecal Egg Count quarantined from the rest of the herd for 21 to 30 days. Reduction Test may be necessary in order to determine They should be treated with anthelmintics from three the efficacy of the anthelmintics. This test, more different classes in order to avoid leaving any worms commonly called FECR test, involves taking fecal present that may be resistant to one of the classes of samples from a random group of animals within the anthelmintics. Using three different drug classes

Purdue Extension • Knowledge to Go  should kill all of the worms present in the animal. level of color in the eyelid. A normal eyelid of a Following deworming, the animal should remain healthy sheep or goat is dark red, indicating that no separate from the herd in a dry lot for 21 days, and a anemia is present and the animal is presumed to be fecal egg count should be performed in order to ensure free of dangerous levels of parasites. The range of that the deworming achieved the desired results. colors used in the FAMACHA system goes from Red, Rotation of dewormers is also a common practice in to reddish pink, to pink, to pinkish white, to white. The attempting to avoid resistance. Past recommendations numbers 1 to 5 are assigned to each of these values, advocated that producers switch between different respectively. Although some dispute remains as to classes of anthelmintics with every deworming. where the cut off for treatment should be, producers However, this practice has now been shown to increase generally treat animals with a score of a 4 or a 5, and resistance by selecting for worms that are resistant to in some cases a 3. Since goats are affected more different drug classes at the same time. With most seriously by internal parasites than sheep, the cut offs anthelmintics, if worms are resistant to one member for treatment in goats may be lower than in sheep to of that drug class, they will be resistant to all of the prevent serious loss from occurring. Treatment also members of that class. The current recommendation is depends on class of animal and the relative that anthelmintic dewormers be rotated on an annual susceptibility of that class of animal (i.e. buck, doe, basis, or until the current drug loses its effectiveness. kid, lamb). Producers can be trained and certified to By using the anthelmintic for a longer period of time, the development of resistance is slowed. It is becoming a common practice to deworm only some of the animals in the herd. This practice is based on the knowledge that in most herds 20 percent of the animals carry approximately 70 to 80 percent of the parasite burden. By only deworming a small portion of the herd, there is a population of worms left in refugia. Refugia refers to the population of worms that are left untreated, and therefore are still susceptible to anthelmintics. By maintaining this sensitive worm population, the anthelmintic resistant genes are diluted among the population, and resistance is slowed down. A system called the FAMACHA system was developed in South Africa based on the refugia concept. It is used as a way to combat resistance and lower the cost to sheep and goat producers of Haemonchus loss, treatment, and control. FAMACHA As was mentioned in the previous section, FAMACHA is a system that was developed in South Africa to aid farmers in combating the problems of parasite resistance and high treatment costs in sheep. The goal of the FAMACHA system is to decrease and delay resistance by only selectively treating the animals in the herd that are showing symptoms of parasite infection. Haemonchus has already been described as a blood sucking parasite that causes severe anemia in its hosts. FAMACHA utilizes the color of the mucous membranes in the lower eyelid to determine the level of anemia that the animal is experiencing. The FAMACHA chart Figure 9: This image is the FAMACHA chart that depicts the eyelid color (see Figure 9) assigns a number from 1 to 5 to each associated with each level of anemia and each FAMACHA score.

Purdue Extension • Knowledge to Go  Fitch, Gerald Q. Internal Parasite Control of Sheep in Oklahoma. Oklahoma State University. Greiner, Scott P. Control of Internal Parasites in Sheep. Virginia Cooperative Extension, May 1998. Hartwig, Nolan, DVM. Control of Internal Parasites of Sheep. Iowa State University. April, 2000. Kaplan, Ray M. DVM, PhD. Responding to the Emergence of Multiple-Drug Resistant Haemonchus contortus: Smart Drenching and FAMACHA©. Department of Medical Microbiology and Parasitology, College of Veterinary Medicine, University of Georgia, 2004. Luginbuhl, J.M. Gastrointestinal Parasite Management of Meat Goats. North Carolina State University, Figure 10: This picture shows a goat having the color of its eyelid October 1998. checked against the FAMACHA chart. Machen, R., Craddock, R. & Craig, T. Monitoring use the FAMACHA system (see Figure 10). The Internal Parasite Infection in Small Ruminants. Texas FAMACHA system can be a valuable tool in helping Agricultural Extension Service. to delay resistance issues in sheep and goat herds. Rook, J.S. DVM. Available Sheep Anthelmintics (Dewormers). Michigan State University. Recommendations for Effective Scarfe, A. David. Approaches to Managing Management of Internal Parasites Gastrointestinal Parasites in Small • Remember that effective management of internal Ruminants. Meat Goat Production Handbook. parasites cannot be accomplished by using only Scarfe, A. David. A New Practical Service to Assist in the one management factor, it is a combination Management of Sheep and Goat Parasites. Meat Goat of factors that will produce the most effective Production Handbook. defense against internal parasites. Scoggins, R.D., DVM. Control of Internal Parasites in • Anthelmintics should be used only to treat Sheep. University of Illinois Extension. June, 2000. animals when necessary, and should be thought Shulaw, W.& Monahan, C. Parasite Control in Sheep: of as a limited resource to be used sparingly. Biologic Approaches for the New Millenium. Ohio • Rotation between different classes of State University. anthelmintics can slow the development of resistance. Southern Region USDA Program on Sustainable Agriculture Research and Education. Smart Drenching • Remember, if a parasite becomes resistant to for Sheep and Goats. one drug in a class, it is probably resistant to all drugs in that class. Terrill, T., Kaplan, R., Larsen, M., Samples O., Miller, J. & Gelaye, S. (2001) Anthelmintic resistance on goat • The FAMACHA system can be used to identify farms in Georgia: efficacy of anthelmintics against which animals are in need of anthelmintic gastrointestinal in two selected goat herds. treatment. , 97, pp 261-268. • Proper pasture and animal management is a key component to managing internal parasites in Umberger, Steve Sheep: Internal Parasite Management. sheep and goat operations. Virginia Tech, May 1997. References Van Wyk, J., Bath, G. The FAMACHA system for managing haemonchosis in sheep and goats by Bagley, Clell V. Internal Parasites. Utah State University clinically identifying individual animals for treatment. Extension. July, 1997. University of Pretoria, 2002. Craddock, F., Machen R. & Craig, T. Management Tips Wells, Ann DVM. Integrated Parasite Management for for Internal Parasite Control in Sheep and Goats. Livestock. ATTRA, April 1999. Texas A&M University. Whittier, W.Dee, DVM; Zajac, Anne; Umberger, Steven Christensen, Karin. Internal Parasites of the Goat. H. Control of Internal Parasites in Sheep. Virginia Scientific Animation and Illustration 2005. State University, October 2003.

Purdue Extension • Knowledge to Go  AS-573-W Managing Internal Parasitism in Sheep and Goats Purdue Extension

New 8/06

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